1. Field of the Invention:
The present invention relates to a speed controller for controlling revolution speed of an upper shaft of a cycle sewing machine.
2. Description of the Prior Art:
A prior art speed controller for controlling revolution speed of an upper shaft of a cycle sewing machine is provided with a disk shaped stop lever cam 10' having an eccentric cam member 27' as shown in FIG. 7. The stop lever cam 10' functions to control the revolution speed of the upper shaft of the cycle sewing machine and has in succession a stop interval 10'a, a low revolution speed interval l1, a high revolution speed interval l2, and a low revolution speed interval l3 whereby the upper shaft at a first end of the low revolution speed interval l1 attains a lower revolution speed in order to prevent occurrence of a condition wherein a thread threaded into a needle at the first stitch is not threaded into the cloth to be woven, this condition being defined as a first stitch omission state.
However, the prior art speed controller for controlling revolution speed of the upper shaft of the cycle sewing machine has a shortcoming in that since an eccentric cam member 27' is unadjustably fixed to the stop lever adjusting cam 10', the low revolution speed interval l1 at the first end cam can not be shortened regardless of the material to be sewn. Consequently, in order to prevent occurrence of the first stitch omission state, it is necessary to use a relatively long sewing cycle.